Ya ayyuha annasu ittaqoo rabbakum inna zalzalata assaAAati shay-on AAatheem (surah Hajj: 1)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(22:1) O people, save yourselves from the wrath of your Lord: the fact is that the earthquake of the Resurrection is a terrible thing. *1

Yaaa ayyuhan naasuttaqoo Rabbakum; inna zalzalatas Saa`ati shai`un `azeem

*1) According to the early commentators, this earthquake will be a prelude to Resurrection. This will probably take place when the earth will begin to rotate in the reverse order, and the sun will rise in the west. In a lengthy Tradition reported by Ibn Jarir, 'Tabarani and Ibn Abi Hatim from Abu Hurairah, the Holy Prophet has stated that when the first Trumpet will be blown, there will be a general confusion; at the second all people will die and at the third they will be brought back to life and presented before Allah. At the first blowing of the Trumpet, the earth will begin to rock like a boat which is beaten about by huge waves, or like a hanging lamp which is moved from side to side by a strong wind.
This condition has been depicted in the Qur'an at several other places. For instance LVI: 6; LXIX: 13-14; LXXIII: 14, 17-18; LXXIX : 6-9 and XCIX: 1-3.
According to other commentators, this earthquake will occur when the dead will be brought back to life and presented before their Lord. Though this is supported by some Traditions, we prefer the first interpretation (in spite of the fact that the Tradition reported by Abu Hurairah is "weak") because that is supported by clear verses of the Qur'an.